ppc/spapr: Add support for implement support for H_SCM_HEALTH

Add support for H_SCM_HEALTH hcall described at [1] for spapr
nvdimms. This enables guest to detect the 'unarmed' status of a
specific spapr nvdimm identified by its DRC and if its unarmed, mark
the region backed by the nvdimm as read-only.

The patch adds h_scm_health() to handle the H_SCM_HEALTH hcall which
returns two 64-bit bitmaps (health bitmap, health bitmap mask) derived
from 'struct nvdimm->unarmed' member.

Linux kernel side changes to enable handling of 'unarmed' nvdimms for
ppc64 are proposed at [2].

References:
[1] "Hypercall Op-codes (hcalls)"
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n220
[2] "powerpc/papr_scm: Mark nvdimm as unarmed if needed during probe"
    https://lore.kernel.org/linux-nvdimm/20210329113103.476760-1-vaibhav@linux.ibm.com/

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Message-Id: <20210402102128.213943-1-vaibhav@linux.ibm.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

2 files changed, 38 insertions, 1 deletions

diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
index b46c369..252204e 100644
--- a/hw/ppc/spapr_nvdimm.c
+++ b/hw/ppc/spapr_nvdimm.c
@@ -31,6 +31,10 @@
 #include "qemu/range.h"
 #include "hw/ppc/spapr_numa.h"
 
+/* DIMM health bitmap bitmap indicators. Taken from kernel's papr_scm.c */
+/* SCM device is unable to persist memory contents */
+#define PAPR_PMEM_UNARMED PPC_BIT(0)
+
 bool spapr_nvdimm_validate(HotplugHandler *hotplug_dev, NVDIMMDevice *nvdimm,
                            uint64_t size, Error **errp)
 {
@@ -467,6 +471,37 @@ static target_ulong h_scm_unbind_all(PowerPCCPU *cpu, SpaprMachineState *spapr,
     return H_SUCCESS;
 }
 
+static target_ulong h_scm_health(PowerPCCPU *cpu, SpaprMachineState *spapr,
+                                 target_ulong opcode, target_ulong *args)
+{
+
+    NVDIMMDevice *nvdimm;
+    uint64_t hbitmap = 0;
+    uint32_t drc_index = args[0];
+    SpaprDrc *drc = spapr_drc_by_index(drc_index);
+    const uint64_t hbitmap_mask = PAPR_PMEM_UNARMED;
+
+
+    /* Ensure that the drc is valid & is valid PMEM dimm and is plugged in */
+    if (!drc || !drc->dev ||
+        spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
+        return H_PARAMETER;
+    }
+
+    nvdimm = NVDIMM(drc->dev);
+
+    /* Update if the nvdimm is unarmed and send its status via health bitmaps */
+    if (object_property_get_bool(OBJECT(nvdimm), NVDIMM_UNARMED_PROP, NULL)) {
+        hbitmap |= PAPR_PMEM_UNARMED;
+    }
+
+    /* Update the out args with health bitmap/mask */
+    args[0] = hbitmap;
+    args[1] = hbitmap_mask;
+
+    return H_SUCCESS;
+}
+
 static void spapr_scm_register_types(void)
 {
     /* qemu/scm specific hcalls */
@@ -475,6 +510,7 @@ static void spapr_scm_register_types(void)
     spapr_register_hypercall(H_SCM_BIND_MEM, h_scm_bind_mem);
     spapr_register_hypercall(H_SCM_UNBIND_MEM, h_scm_unbind_mem);
     spapr_register_hypercall(H_SCM_UNBIND_ALL, h_scm_unbind_all);
+    spapr_register_hypercall(H_SCM_HEALTH, h_scm_health);
 }
 
 type_init(spapr_scm_register_types)
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index bf7cab7..d2b5a9b 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -538,8 +538,9 @@ struct SpaprMachineState {
 #define H_SCM_BIND_MEM          0x3EC
 #define H_SCM_UNBIND_MEM        0x3F0
 #define H_SCM_UNBIND_ALL        0x3FC
+#define H_SCM_HEALTH            0x400
 
-#define MAX_HCALL_OPCODE        H_SCM_UNBIND_ALL
+#define MAX_HCALL_OPCODE        H_SCM_HEALTH
 
 /* The hcalls above are standardized in PAPR and implemented by pHyp
  * as well.